The correct option is C discordant
The word 'unanimous' refers to being fully in agreement.
Option A, uncertain refers to being not completely sure or confident of something.
Option B, partial refers to favouring one side of the dispute over another.
Option C, discordant refers to disagreeing or incongruous.
Option D, different refers to being novel and unusual.
Thus, according to the meaning, the word 'discordant' is the opposite of the word 'unanimous'.